Radiation heat collector

ABSTRACT

In a heat collector comprising a linear tubular heat collector member defining an internal passage for conducting fluid a reflector having a reflecting surface partly surrounding the heat collector member and a heat insulating member provided in association with the reflector. The insulating member is typically directly attached to the reflector. The heat insulating member improves the thermal efficiency of the heat collector.

TECHNICAL FIELD

[0001] The present invention relates to a radiation heat collectortypically employed to collect solar heat to fluid media such as water.

BACKGROUND OF THE INVENTION

[0002] Conventionally, various forms of solar heat collectors have beenproposed. Typically, a solar heat collector comprises a tubular heatcollector member for conducting water that is to be heated, and areflector for converging incident solar light upon the heat collectormember. The reflector may consist of sheet metal having a reflectivesurface which is formed into a per se known CPC (compound parabolicconcentrator) shape and reinforced by a plurality of ribs. The CPC isgiven as a combination of a pair of parabolic segments at an angle whichis joined by an involute curve. The CPC allows an incident solar ray toefficiently converge upon the heat collector member placed in a bottompart thereof over a wide range of incident angle. For details of theCPC, reference should be made to U.S. Pat. No. 4,002,499 issued Jan. 11,1977 to R. Winston.

[0003] However, because the CPC surface has a relatively complexprofile, it was difficult to form sheet metal into the desired shape,and the material for the reflector was required to have a significantthickness to ensure an adequate rigidity and maintain the originalshape. Therefore, the manufacturing cost was high, and the reflector wasundesirably heavy. Because such a solar heat collector is a consumeritem, and typically placed on a roof, such disadvantages are highlydetrimental for the market acceptability.

[0004] Furthermore, the thermal efficiency of a solar heat collector ishighly crucial in making the solar heat collector acceptable in themarket because it has to compete with other forms of heat sources suchas gas and electricity. Heat insulation for the collected heat is animportant factor in determining the thermal efficiency, but again it hasto be accomplished without substantially increasing the cost and weightof the solar heat collector.

BRIEF SUMMARY OF THE INVENTION

[0005] In view of such problems of the prior art and recognitions by theinventors, a primary object of the present invention is to provide aradiation heat collector which can improve the thermal efficiency byfavorably insulating the collected heat.

[0006] A second object of the present invention is to provide aradiation heat collector which is light in weight.

[0007] A third object of the present invention is to provide a radiationheat collector which is economical to manufacture.

[0008] A fourth object of the present invention is to provide aradiation heat collector which is provided with a reflector which can begiven with a precise surface profile, and can maintain it during use.

[0009] According to the present invention, such objects can beaccomplished by providing a heat collector, comprising: a linear tubularheat collector member defining an internal passage for conducting fluid;a reflector having a reflecting surface partly surrounding the heatcollector member; and a heat insulating member provided in associationwith the reflector. The insulating member is typically directly attachedto the reflector. The heat insulating member improves the thermalefficiency of the heat collector.

[0010] The insulating member make take the form of a substantiallytransparent module cover which covers an open end of the reflector. Thecover allows the radiation input freely while preventing the dissipationof the heat collected in the heat collector member.

[0011] Alternatively or additionally, the insulating member may comprisea thermally insulating layer attached to a backside of the reflector. Itis advantageous to make use of a part of the reflector as the insulatingmember. For instance, the reflector may comprise a support memberdefining a surface profile for a reflective surface, and a reflectivelayer formed over the surface profile to define a reflective surface,the support member serving as the thermally insulating layer.Alternatively, the reflector may comprise a stamp formed or roll formedsheet metal defining a reflective surface, and a support membersupporting the stamp formed sheet metal from backside thereof, thesupport member serving as the thermally insulating layer.

[0012] The reflector may also comprise a stamp formed or roll formedsheet metal defining a reflective surface, and a plurality of ribsformed on a back side thereof for reinforcement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Now the present invention is described in the following withreference to the appended drawings, in which:

[0014]FIG. 1 is a perspective view of a heat collector embodying thepresent invention;

[0015]FIG. 2 is a cross sectional view showing one of the heat collectormodules;

[0016]FIG. 3 is a perspective view of a second embodiment of the presentinvention;

[0017]FIG. 4 is a cross sectional view showing one of the heat collectormodules of the heat collector illustrated in FIG. 3;

[0018]FIG. 5 is a cross sectional view of the heat collector illustratedin FIG. 3;

[0019]FIG. 6 is a perspective view of a third embodiment of the presentinvention; and

[0020]FIG. 7 is a cross sectional view showing one of the heat collectormodules of the heat collector illustrated in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021]FIG. 1 generally illustrates a radiation heat collector in theform of a solar water heater embodying the present invention. This heatcollector comprises a casing 1 in the form of a box having an open topend, and a plurality of heat collector modules 2 placed one next toanother inside the casing 1. Each heat collector module 2 comprises aheat collector member 3 consisting of a tubular member, and a reflector4 for reflecting solar light onto the heat collector member 3. Thetubular heat collector members 3 are connected to one another in seriesvia a connecting pipe 3 a, and one end of the serial connection isconnected to a cool water source via a pump or the like while the otherend thereof is connected to a user of hot water such as a storage tankand a radiator. If desired, the tubular heat collector members 3 mayalso be connected to one another in parallel. It is also possible tocombine serial and parallel connections as desired.

[0022] The open end of the casing 1 may be closed by a sheet or aplurality of sheets of glass or other transparent material 5 tothermally insulate the interior of the casing 1. It has been proven tobe advantageous to use a double glass pane, optionally having anevacuated intermediate layer. If desired, the interior of the casing 1may be evacuated for an improved thermal insulation.

[0023] Referring to FIG. 2, each reflector 4 is formed by moldingplastic material such as foamed urethane or the like having a high levelof thermal insulation, and is provided with a reflective surface 4 adefined by a reflective layer 6. The reflective layer 6 may be formed byany one of a number of known methods including, not exclusively,plating, ion plating and other physical or chemical film formingprocesses, and coating. According to this arrangement, thereproducibility and stability of the shape of the reflective surface canbe ensured more easily and more economically than the more conventionalarrangement using stamp formed sheet metal to form the reflector. Thesurface contour of the reflective surface 4 a is determined by thesurface profile of the underlying surface of the main body of thereflector 4 made of thermally insulating material.

[0024] The reflective surface 4 a of each reflector 4 is formed as a perse known CPC (compound parabolic concentrator) shape. The CPC is givenas a combination of a pair of parabolic segments (side segments) 4 b atangle θ which is joined by an involute curve (bottom segment) 4 c. Thebottom segment 4 c is provided with a central ridge 4 d. The CPC allowsan incident solar ray to efficiently converge upon the heat collectormember 3 placed in a bottom part thereof over a wide range of incidentangle. For details of the CPC, reference should be made to U.S. Pat. No.4,002,499 issued Jan. 11, 1977 to R. Winston. The central ridge 4 d inthe bottom part of each reflector 4 ideally touches the heat collectormember 3, but in practice is spaced from the heat collector member 3 sothat the loss of heat from the heat collector member 3 due to such acontact may be avoided.

[0025] Each reflector 4 was shaped like a trough defining a CPCreflective surface in the illustrated embodiment, but the reflectivesurface 4 a may consist of a simple parabolic surface or anyapproximately parabolic surface. Because each reflector is thermallyinsulated, dissipation of heat via the casing 1 can be minimized, andthe fabrication process is simplified because no separate thermalinsulation material is required.

[0026] FIGS. 3 to 5 show a second embodiment of the present invention.This heat collector comprises a casing 11 in the form of a box having anopen top end, and a plurality of heat collector modules 12 placed onenext to another inside the casing 11. Each heat collector module 12comprises a heat collector member 13 consisting of a tubular member, anda reflector 14 for reflecting solar light onto the heat collector member13. The tubular heat collector members 13 are connected to one anotherin series via a connecting pipe 13 a, and one end of the serialconnection is connected to a cool water source via a pump or the likewhile the other end thereof is connected to a user of hot water such asa storage tank and a radiator.

[0027] The open end of the casing 11 is closed by a cover 15 consistingof glass or other substantially transparent material. Thus, the interiorof the casing 11 is entirely enclosed. The reflectors 14 of the heatcollector modules 12 may each consist of stamp formed or roll formedsheet metal having a reflective surface which is formed into a per seknown CPC (compound parabolic concentrator) shape and reinforced by aplurality of ribs 14 a.

[0028] As best shown in FIG. 4, the open upper end of each heatcollector module 12 is closed by a planar module cover 17 made of glassor other substantially transparent material, and the interior of eachheat collector module 12 is entirely enclosed. This prevents heat fromdissipating out of the heat collector module 13.

[0029] As best shown in FIG. 5, a layer of thermally insulating material16 consisting foamed plastic, mineral fibers and other known thermallyinsulating material is placed in a bottom part of the casing 11, andeach heat collector module 12 is snugly received in the complementaryrecesses formed on the surface of the thermally insulating layer 16.

[0030]FIGS. 6 and 7 show a third embodiment of the present invention. Inthis case, no casing is used, and a plurality of heat collector modules22 are arranged in parallel to one another with their end portionsaligned along either side. A pair of connecting pipe covers 25 a and 25b are arranged on either side of the heat collector module assembly.Each heat collector module 23 comprises a tubular heat collector member23 and a reflector 24 for reflecting solar light onto the heat collectormember 23. The heat collector modules 22, more specifically thereflectors 24, are each attached to the connecting pipe covers 25 a and25 b at either end thereof so that these connecting pipe covers 25 a and25 b retain the shape of the entire assembly.

[0031] The tubular heat collector members 13 are connected to oneanother in series via a connecting pipe 23 a, and one end of the serialconnection is connected to a cool water source via a pump or the likewhile the other end thereof is connected to a user of hot water such asa storage tank and a radiator.

[0032] Each reflector 24 is formed by stamp forming or roll formingsheet metal, and its back side is attached, via a bonding agent or thelike, to a complementary surface of a support member 26 formed by moldedplastic material such as foamed urethane or the like having a high levelof thermal insulation and capability to retain the shape of thereflector 24. The reflective surface 24 a of each reflector 24 is formedas a per se known CPC (compound parabolic concentrator) shape. As bestshown in FIG. 7, the open upper end of each heat collector module 22 isclosed by a planar module cover 27 made of glass or other substantiallytransparent material, and the interior of each heat collector module 22is entirely enclosed. This prevents heat from dissipating out of theheat collector module 22.

[0033] The interior of each connecting pipe cover 25 a and 25 b isappropriately insulated by using foamed plastic, mineral fibers or thelike. The connecting pipe covers 25 a and 25 b have the additionalfunction of protecting the connecting pipes 23 from external influencessuch as moisture and impacts.

[0034] Although the present invention has been described in terms of apreferred embodiment thereof, it is obvious to a person skilled in theart that various alterations and modifications are possible withoutdeparting from the scope of the present invention which is set forth inthe appended claims.

1. A heat collector, comprising: a linear tubular heat collector memberdefining an internal passage for conducting fluid; a reflector having areflecting surface partly surrounding said heat collector member; and aheat insulating member provided in association with said reflector.
 2. Aheat collector according to claim 1, wherein said insulating member isdirectly attached to said reflector.
 3. A heat collector according toclaim 2, wherein said insulating member comprises a substantiallytransparent module cover which covers an open end of said reflector. 4.A heat collector according to claim 3, wherein said insulating membercomprises a thermally insulating layer attached to a backside of saidreflector.
 5. A heat collector according to claim 4, wherein saidreflector comprises a support member defining a surface profile for areflective surface, and a reflective layer formed over said surfaceprofile to define a reflective surface, said support member serving assaid thermally insulating layer.
 6. A heat collector according to claim4, wherein said reflector comprises a stamp formed or roll formed sheetmetal defining a reflective surface, and a support member supportingsaid stamp formed sheet metal from backside thereof, said support memberserving as said thermally insulating layer.
 7. A heat collectoraccording to claim 4, wherein said reflector comprises a stamp formed orroll formed sheet metal defining a reflective surface, and a pluralityof ribs formed on a back side thereof for reinforcement.